Data centers are large computer rooms that are organized in so-called hot aisles and cold aisles. Server racks separate the hot aisles from the cold aisles, with the servers in the server racks typically arranged to draw cold air from the cold aisles to cool the servers in the racks and expel the heated air into the hot aisles. A computer room air conditioning (CRAC) unit draws in air from the hot aisles, typically through ceiling tiles of the computer room and returns the cooled air to the cold aisles via perforated floor tiles and/or grates in the cold aisles. The conduits required for the air flow from and to the CRAC unit are typically defined by a suspended ceiling and a raised floor, as is well-known per se.
Data centers require large amounts of energy to operate. A substantial part of this energy is being consumed by the CRAC unit. As is well-known, the efficiency of air conditioning units such as CRAC units depends on the temperature of the inbound air, i.e. the air drawn from the hot aisles. In case of low server activity, the air of the associated hot aisle may have a relatively low temperature, which therefore negatively impacts on the efficiency of the CRAC unit. This is undesirable, as this pushes up the energy consumption of the data center as a whole, which not only increases the operation cost of the data center but also increases the risk of black-outs if the energy demand of the data center cannot be met, which is highly undesirable. It is therefore desirable to try and improve the energy efficiency of data centers.
U.S. Pat. No. 8,156,753 B2 discloses a data center cooling solution providing techniques for using baffles, doors and roof sections to prevent warm air from being entrained into a cold aisle in a data center, wherein the data center generally contains an air cooling system and a raised floor structure. The raised floor structure is configured to deliver cool air into the data center through a plurality of grates and perforated tiles in the floor. Electronic equipment racks are disposed around the grates and perforated tiles, such that the front faces of the equipment racks face the grates and perforated tiles. A collection of baffles, doors or roof sections inhibit the mixing of the cool air delivered by the air cooling system and the warm air exhausted by the electronic equipment. This improves cooling of the servers and therefore increases the temperature gradient between the hot aisles and cold aisles. However, this solution does not address the problem of CRAC inefficiency if this temperature gradient is small, e.g. because of low server activity.
US 2011/0303406 A1 discloses a computer room air-conditioning system including a temperature detection unit which is provided for each of a front and a back of each rack, and which measures air temperatures at the front and the back of the rack. A control device for acquiring a measured temperature by each temperature detection unit and for performing control based on the measured temperature is also present. With the configuration, the control device includes a temperature difference calculation unit for calculating a temperature difference between cool air at the front and warm air at the back of each rack based on each measured and acquired temperature; and a heating element, i.e. server, cooling control unit for controlling by adjustment an amount of flow of cool air from the underfloor space to the computer room based on the calculated temperature difference. This improves the energy efficiency of the data center because the air flow to and from the CRAC unit is reduced for small temperature gradients. Nevertheless, this still requires the CRAC unit to operate at reduced efficiency, albeit at reduced air volumes.